No Room for Windows.old - Upgrade fails - ideas?

Even after Microsoft says you're "Good to Go" with your Win 10 upgrade, [only] early in the install it adds another requirement for 5 GB of free disk space. I'm assuming this is for the temporary "roll back" file.

Well, I don't have a spare 5 Gigs.

I have a HP Mini that I wanted to use for a Win 10 GUI test look, all "tests" showed it was OK. However, it only has a 15 Gb hard drive, with 13.5 Gb occupied by the Windows folder. I've reclaimed all the space I think I can (DiskMgr), including clearing the old update info in Windowsxs, and even compressed the drive. All extra apps have been uninstalled with a 3rd party uninstaller to clear out any leftover bits, and defragged/cleared under the chicken soup protocol. All that got me was another 765Mb.

Any ideas on how to get the installer to skip the rollback file? Perhaps something like the old time command line switches?

Otherwise, I'll just reinstall Win7 and return the Netbook to service as my internet radio tuner.